This application claims the priority of German patent document 10 2007002188.9-51, filed Jan. 16, 2007, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a hybrid vehicle having an internal-combustion engine and an electric motor.
To comply with the increasingly stricter environmental laws, motor vehicles are currently normally equipped with a filtering device which is arranged in a fuel tank ventilator pipe. This filtering device, which preferably has activated carbon as the filtering material, filters hydrocarbons out of a tank ventilation current, so that no hydrocarbons (or only a very small amount of hydrocarbons) reach the environment. However, if the filtering material is saturated, no additional hydrocarbons can be absorbed, and the filtering device loses its effect. In order to keep the filtering device operational for a long period of time, the latter is flushed from time to time and the filtering material is thereby regenerated.
The flushing current for regenerating the filtering material is fed to an intake path of the internal-combustion engine, so that the hydrocarbons flushed out of the filtering material can be burnt in the internal-combustion engine in a manner protecting the environment. However, in the case of motor vehicles having a hybrid drive, it is problematic that the internal combustion engine does not operate continuously but is switched off, particularly during a purely electromotive drive. In the switched-off condition, the hydrocarbons flushed out of the filtering device into the intake path cannot be burned, and this concept is therefore suboptimal in the case of hybrid vehicles.
One object of the present invention is to provide a different or improved filtering arrangement for a hybrid vehicle which is distinguished particularly by a lower pollutant emission.
This and other objects and advantages are achieved by the hybrid vehicle and filtering apparatus according to the invention, which is based on the general idea of providing a hybrid vehicle (having an internal-combustion engine, an electric motor as well as a tank ventilation system) with a control device that starts the internal-combustion engine when there is a simultaneous requirement to flush or regenerate the filtering device during a purely electromotive drive of the hybrid vehicle. As a result, the hydrocarbons flushed back from the filtering device are fed to the combustion in the internal-combustion engine.
The filtering device is arranged in a tank ventilation pipe, which leads from a tank into the environment and can be shut off by means of a valve device arranged in the suction pipe between the filtering device and an intake path of the internal-combustion engine. If a filtering material of the filtering device is saturated with hydrocarbons, the control device for flushing the filtering device actuates the valve device and thereby permits the above-mentioned feeding of hydrocarbons present in the pipes and in the filtering device to the internal-combustion engine.
Combustion of the hydrocarbons present in the pipe or in the filtering device can of course take place only when the internal-combustion engine is running at least in the standing gas-driven condition. However, in the case of hybrid-operated motor vehicles, the internal-combustion engine is switched off during an electromotive drive condition. Thus, the control device according to the invention is constructed such that, in the electric operation of the hybrid vehicle, it switches on or connects the internal-combustion engine as a function of a loading condition of the filtering device. Thus, if the hybrid vehicle is operated electrically and, for example, a sensor detects that the filtering material is saturated with hydrocarbons, the control device will, on the one hand, open the valve device in the suction pipe and in the tank ventilation pipe and, on the other hand, start the internal-combustion engine which will then burn the hydrocarbons fed to it. In this manner, hydrocarbon emission (and thus pollutant emissions) can therefore clearly be reduced in the case of hybrid-operated motor vehicles.
According to another feature of the invention, a vacuum accumulator is provided in the intake path of the internal combustion engine. When the valve devices are open, the vacuum accumulator permits flushing of the filtering device, even when the internal-combustion engine is switched off. This vacuum accumulator preferably contains a vacuum volume sufficient for flushing the filtering device and can be opened as required. This can also take place in the purely electromotive operating condition of the hybrid vehicle, in which then the control device, on the one side, opens the valve device in the suction pipe and in the tank ventilation pipe and, on the other side, in a communicating manner, connects the vacuum accumulator with an intake path of the internal-combustion engine. As a result of the vacuum existing in the vacuum accumulator, the hydrocarbons are taken in from the suction pipe and from the filtering material of the filtering device and are stored in the intake path or in the vacuum accumulator until the internal-combustion engine is started. When the internal-combustion engine is started in a later operating condition, the hydrocarbons stored in the vacuum accumulator and in the intake path can be fed to the combustion process in the internal-combustion engine. This variant permits flushing or a regeneration of the filtering material present in the filtering device even when the internal-combustion engine is switched off.
In an advantageous further embodiment of the invention, a valve is arranged between the filtering device, on the one side, and the fuel tank on the other side, and also a pumping device is provided which can admit pressure to the fuel tank when the valve device is closed. In addition, a sensor device is provided which can detect a hydrocarbon concentration and/or a pressure in the fuel tank. By means of these devices, a leak test of the fuel tank can be carried out by closing the valve device and admitting pressure to the fuel tank by means of the pumping device. After switching-off the pumping device, the sensor device determines a pressure drop as a function of time, and can draw a conclusion on the tightness of the tank system by way of the thus determined value.
Simultaneously, the admission of pressure to the fuel tank has the important advantage that a transition from a liquid to a gaseous condition of the fuel is made difficult and, as a result, the fuel will clearly evaporate less rapidly. It would therefore be possible to pressurize the fuel tank during a purely electromotive drive and thereby make a gassing-out of hydrocarbons from the fuel at least difficult.
It is understood that the above-mentioned characteristics and the characteristics to be explained in the following can be used not only in the respective indicated combination but also in other combinations or alone without leaving the scope of the present invention.